Medical treatment of several illnesses requires continuous drug infusion into various body compartments, such as subcutaneous and intra-venous injections. Diabetes mellitus (DM) patients, for example, require the administration of varying amounts of insulin throughout the day to control their blood glucose levels. In recent years, ambulatory portable insulin infusion pumps have emerged as an alternative to multiple daily syringe injections of insulin, initially for Type 1 diabetes patients and subsequently for Type 2 diabetes patients. These pumps, which deliver insulin at a continuous (or periodic) basal rate, as well as in bolus volumes, were developed to liberate patients from repeated self-administered injections, and to allow them to maintain a normal or near-normal daily routine. Both basal and bolus volumes are generally delivered in precise doses, according to individual prescription, because an overdose or under-dose of insulin could be fatal.
The first generation of portable insulin pumps includes “pager like” devices with a reservoir contained within a housing. A long tube is provided for delivering insulin from the pump attached to a patient's belt to a remote insertion site. Examples of such devices are disclosed, for example, in U.S. Pat. Nos. 3,631,847, 3,771,694, 4,657,486 and 4,544,369, the contents of all of which are hereby incorporated by reference in their entireties. These devices represent an improvement over the requirement of multiple daily injections, but have drawbacks, among which are the large size and weight of the devices, the long tubing which limits the daily activities of the devices' users, and lack of discreetness.
To avoid the limitations associated with first generation infusion pumps, a new concept was proposed, which was implemented in second generation pumps. The new concept is predicated on the use of a remote contained skin-adherable device with a housing having a bottom surface adapted to be in contact with the patient's skin, a reservoir disposed within the housing, and an injection needle in fluid communication with the reservoir. These skin adherable devices are configured to generally be replaced every 2-3 days, similarly to currently available pump infusion sets. This paradigm is described, for example, in U.S. Pat. Nos. 4,498,843, 5,957,895, 6,589,229, 6,740,059, 6,723,072 and 6,485,461, the contents of all of which are hereby incorporated by reference in their entireties. These second generation skin securable devices also have several drawbacks. For example the entire device has to be typically disposed-of every 2-3 days, resulting in the devices' expensive components (such as electronics, driving mechanism, etc.) also being disposed of.
Third generation skin-adherable devices were developed to avoid the cost issues associated with second generation devices and to extend patient customization. An example of such a device was described in co-owned/co-pending. U.S. Patent publication no. 2007-0106218 and International Patent publication no. WO/2007/052277, the contents of all of which are hereby incorporated by reference in their entireties. Such a third generation device contains a remote control unit and a skin-adherable patch unit (also referred to as “dispensing patch unit” or “dispensing unit”) that may include two parts: (1) a reusable part containing the electronics, at least a portion of the driving mechanism and other relatively expensive components, and (2) a disposable part containing the reservoir and, in some embodiments, at least one power source (e.g., a battery). A tube can also be provided which delivers the fluid from the reservoir to an outlet port that contains a connecting lumen.
This concept can provide a cost-effective skin-adherable infusion device and enables device versatility in terms of the various reservoir sizes that may be used, the various needle and cannula types that may be used, etc.
A skin-adherable fluid (e.g., insulin) delivery device was also disclosed in co-owned, co-pending U.S. patent application Ser. No. 11/989,681 and International Patent publication no. WO/2008/012817, both filed Jul. 24, 2007 and both claiming priority to U.S. Provisional Patent Applications Nos. 60/833,110, filed Jul. 24, 2006, and 60/837,877, filed Aug. 14, 2006, both entitled “Systems, Devices, and Methods for Fluid/Drug Delivery”, the contents of all of which are hereby incorporated by reference in their entireties.
A fourth generation infusion device is disclosed in co-owned, co-pending U.S. Patent publication no. 2008-0215035 and International Patent publication no. WO/2008/078318, both filed Dec. 20, 2007, claiming priority to U.S. Provisional Patent Application No. 60/876,679, filed Dec. 22, 2006, entitled “Systems, Devices, and Methods for Sustained Delivery of a Therapeutic Fluid”, the contents of all of which are hereby incorporated by reference in their entireties.
Fourth generation devices are configured as dispensing units that can be disconnected and reconnected to a skin-adherable cradle unit. Fourth generation skin-securable dispensing units can be remotely controlled and/or can be operated by a user interface (e.g., a buttons-based interface) that are located on the dispensing unit's housing (and/or, in some embodiments, on the reusable part) as disclosed, for example, in the co-owned, co-pending International Patent publication no. WO/2009/013736, filed Jul. 20, 2008, claiming priority to U.S. Provisional Patent Application No. 60/961,527, and entitled “Manually Operable Portable Infusion Pump”, and International Patent publication no. WO/2009/016636, filed Jul. 31, 2008, claiming priority to U.S. Provisional Application Ser. Nos. 60/963,148 and 61/004,019, and entitled “Portable infusion device with means for monitoring and controlling fluid delivery”, the contents of all of which are hereby incorporated by reference in their entireties.
Co-owned/co-pending U.S. Patent publication no. 2007-0191702, the content of which is hereby incorporated by reference in its entirety, discloses a device that includes a dispensing patch unit (e.g., an insulin dispensing patch) and an analyte sensor (e.g., a continuous glucose monitor). This type of dual function device has a similar configuration to that outlined above and can also be disconnected and reconnected from and to the skin at patient's discretion.
In some embodiments, fluid delivery devices include a notification component (also referred to as a notifier or indicator) for notification purposes, e.g., to notify the user that fluid delivery has started, and/or for alerting purposes, e.g., to alert the user in case of mechanical malfunction or of low battery status. Such a notification component can be located in a skin-securable dispensing unit and/or in a remote control. The notification component can provide auditory output (e.g., a buzzer), visual output (e.g., the notification component can include a display, flashing lights, etc.) or provide tactile output (e.g., a vibrator). An auditory notification component (also referred to as “Buzzer”) can employ, for example, a piezoelectric element or a magnetic element, which is typically disposed within a resonance chamber (i.e., a cavity defined by interior surfaces that reflect acoustic/sound waves) in order to amplify the sound generated by the element.
A number of different forms of buzzers, employing piezoelectric elements or transducers to generate a relatively piercing and noticeable audible tone when energized with relatively little power, have come into use. Such systems are activated at or near the resonant frequency of the vibrating piezoelectric element to achieve the most efficient use of available electrical energy and greatest audible output.
In a device for delivering a therapeutic fluid (e.g., insulin) to the body of a patient, it is generally important to maximally amplify the sound generated by the buzzer, since the consequence of not hearing the generated sound can be hazardous, for example, in case of an alert generated upon occlusion detection. The generated sound can be maximally amplified by placing the buzzer inside a suitable resonance chamber and activating it at or near the resonant frequency of the piezoelectric element, i.e., the frequency at which the amplitude of the piezoelectric element's oscillation is the greatest.
However, individual piezoelectric elements often vary in precise resonant frequency, and thus, a manufacturer's data sheet typically specifies only a frequency range within which the actual resonant frequency of the piezoelectric element is guaranteed to lie (e.g. 4.0±0.5 KHz). In addition, placing the piezoelectric element inside a resonance chamber may further affect the resonant frequency of the individual piezoelectric element and contribute to the variation in precise resonant frequency, for example, due to different methods of supporting the element within the chamber (e.g., edge support, node support, etc.). Furthermore, the resonant frequency of a single piezoelectric element itself may vary due to such factors as aging, varying temperature and humidity conditions, etc.
In view of this, self-calibrating systems for determining the actual resonant frequency of an individual piezoelectric element/transducer and for driving/activating the element/transducer at its actual resonant frequency have been proposed. Such a system was described, for example, in U.S. Pat. No. 4,275,388, the content of which is hereby incorporated by reference in its entirety. The system described in that patent, as well as other known self-calibrating systems, is generally implemented using a feedback mechanism (e.g., a feedback electrode). In some embodiments, the feedback mechanism is connected to the piezoelectric element that generates a feedback signal representative of the amount of flexing of the element when driven at different frequencies. The optimum driving frequency is then determined based on the feedback signal.
Despite the hazardous consequences of inefficient buzzers, existing fluid delivery devices generally do not employ such self-calibrating systems. Furthermore, the existing self-calibration systems, which require the use of feedback mechanisms, are not suitable for skin-securable miniature fluid delivery devices due to some of the following reasons:                The need for additional components/modules (e.g., a feedback electrode, contacts) requires enlargement of the device and creates undesirable limitations regarding the spatial arrangement of the buzzer, and other components, within the delivery device.        The piezoelectric buzzer (also referred to as “piezoelectric diaphragm”) typically includes a piezoelectric plate (e.g., a ceramic plate, a crystal plate) having electrodes on both sides (together referred to as “piezoelectric element”), and a metal plate (e.g., brass, stainless steel, etc.). Connecting a feedback mechanism to the piezoelectric element reduces the efficiency of the buzzer as it requires a size reduction of one of the element's electrodes.        Implementation of the described self-calibration systems increases the cost (and thus the price to the consumer) of the device as additional components are required.        